Device Tree: Adding Alias for GPIO Controller Node causes DTC Warning

[Jannik-M91]

Not sure if this is a bug or I am doing something wrong.

Whenever I add an alias for a GPIO controller node:

aliases {
	my-gpio = &gpio0;
};

...

gpio0: gpio@40014000 {
	compatible = "raspberrypi,pico-gpio";
	reg = <0x40014000 DT_SIZE_K(4)>;
	interrupts = <13 RPI_PICO_DEFAULT_IRQ_PRIORITY>;
	gpio-controller;
	#gpio-cells = <2>;
	status = "disabled";
	ngpios = <30>;
};

I get the following warning from the device tree compiler:

Warning (gpios_property): /aliases:my-gpio: property size (19) is invalid, expected multiple of 4

I have no idea where the number 19 is coming from. I can use the alias in my code just fine so I can probably ignore the warning. I would still like to understand where it comes from though and I do not like having warnings in my compile output as it can confuse other people who are working on the project.

Thanks for any suggestions!

Edit: I found another occurrence of this issue on the Nordic forums: https://devzone.nordicsemi.com/f/nordic-q-a/113004/warning-gpios_property-during-build-of-slm-shell-sample

The size (in my case 19) seems to be derived from the length of the node path which does not sound useful to me.

[ldomaigne]

Properties xxx-gpio and xxx-gpios have a special meaning ( ie. defines GPIOs ). Consider renaming your property my-gpio to mygpio (without dash) for instance, and see if that helps:

aliases {
	mygpio = &gpio0;
};

You need to change your code accordingly when accessing the alias.

[Jannik-M91]

Thanks! That did indeed fix the issue.

Wouldn't it be better if that "magic GPIO syntax" would not be used inside the alias block as it does not make sense to define a GPIO in that block?

[ldomaigne]

Yes, you're making a good point. Might be not necessarily easy to implement, because of the historical baggage we've inherited.